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Subject[PATCH RFC v1 08/18] x86/hyperv: handling hypercall page setup for root
Date
When Linux is running as the root partition, the hypercall page will
have already been setup by Hyper-V. Copy the content over to the
allocated page.

The suspend, resume and cleanup paths remain untouched because they are
not supported in this setup yet.

Signed-off-by: Lillian Grassin-Drake <ligrassi@microsoft.com>
Signed-off-by: Sunil Muthuswamy <sunilmut@microsoft.com>
Signed-off-by: Nuno Das Neves <nudasnev@microsoft.com>
Co-Developed-by: Lillian Grassin-Drake <ligrassi@microsoft.com>
Co-Developed-by: Sunil Muthuswamy <sunilmut@microsoft.com>
Co-Developed-by: Nuno Das Neves <nudasnev@microsoft.com>
Signed-off-by: Wei Liu <wei.liu@kernel.org>
---
arch/x86/hyperv/hv_init.c | 26 ++++++++++++++++++++++++--
1 file changed, 24 insertions(+), 2 deletions(-)

diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
index 0eec1ed32023..26233aebc86c 100644
--- a/arch/x86/hyperv/hv_init.c
+++ b/arch/x86/hyperv/hv_init.c
@@ -25,6 +25,7 @@
#include <linux/cpuhotplug.h>
#include <linux/syscore_ops.h>
#include <clocksource/hyperv_timer.h>
+#include <linux/highmem.h>

/* Is Linux running as the root partition? */
bool hv_root_partition;
@@ -448,8 +449,29 @@ void __init hyperv_init(void)

rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
hypercall_msr.enable = 1;
- hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg);
- wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+
+ if (hv_root_partition) {
+ struct page *pg;
+ void *src, *dst;
+
+ /*
+ * Order is important here. We must enable the hypercall page
+ * so it is populated with code, then copy the code to an
+ * executable page.
+ */
+ wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+
+ pg = vmalloc_to_page(hv_hypercall_pg);
+ dst = kmap(pg);
+ src = memremap(hypercall_msr.guest_physical_address << PAGE_SHIFT, PAGE_SIZE,
+ MEMREMAP_WB);
+ memcpy(dst, src, PAGE_SIZE);
+ memunmap(src);
+ kunmap(pg);
+ } else {
+ hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg);
+ wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
+ }

/*
* Ignore any errors in setting up stimer clockevents
--
2.20.1
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